This invention relates to a device for forming graphics such as letters, numbers and symbols and in one aspect to a device for forming graphics by light exposure through a template onto a strip material.
U.S. Pat. No. 3,914,775 describes a device that forms graphics which are made immediately visible along a strip material. The device is adapted to use a composite strip material, more completely described in U.S. Pat. No. 4,123,578 (the content whereof is incorporated herein by reference). Briefly, that strip material comprises a receiving web carrying a firmly adhered layer of waxy material having a predetermined softening temperature above normal room temperature, and a donor web carrying a lightly adhered layer of colored microgranules in face-to-face contact with the layer of waxy material. One of the layers bears a radiation absorbing pigment. When the layers are positioned in intimate contact, and the strip material is momentarily exposed to intense radiation in a graphic pattern, the radiated pigment is heated and softens the adjacent portion of the waxy layer. The softened waxy material adheres to the microgranules upon solidification, and when the webs are separated the colored microgranules transfer to the receiving web in accordance with the pattern of radiation.
The device described in U.S. Pat. No. 3,914,775 includes means for positioning a portion of the strip material at an exposure station with the layers in face-to-face contact and a thin template having a radiation transmissive window in the shape of a graphic to be formed mounted to register the window at the exposure station adjacent the strip material. Means are provided at the exposure station for pressing the strip material and template in intimate contact, and a lamp is provided for irradiating the clamped strip material through the window to form a graphic on the strip material which corresponds to the window by pivotal movement of a lamp arm at the end of which the lamp is mounted from a normal position spaced from the exposure station to afford visible inspection of the template and the portion of the strip material at the exposure station, and an expose position with the lamp closely adjacent the exposure station at which expose position the lamp is operated.
While the device described in U.S. Pat. No. 3,914,775 can form graphics having such good resolution that even half-tone photographs can be reproduced, it requires the operator to manually set the spacing between successive graphics formed along the strip material with the aid of guide marks on the template at the exposure station. Also, that device requires that the portion of the template in which the window is located be positioned under a transparent plate fixed to a frame of the device at the exposure station, adjacent a movable plunger in the base of the device for pressing the strip material and template portion against the plate. In one embodiment that disadvantage is reduced by using a circular template having a plurality of windows in circular array about its periphery, and rotatably mounting the circular template on the device so that any one of the windows can be rotated into position at the exposure station. Such circular templates, however, are very large for the amount of windows provided thereon, and thus are wasteful of both template material for the manufacturer and storage space for the user. While U.S. Pat. No. 3,828,359 describes a device of the type described above that uses more compact rectangular templates, that template contains only one graphic, is in the form of a slide, and requires the operator to perform the task of inserting the slide under the glass plate for each use of the device.
Also, both of these templates require the operator to visually evaluate spacing between the last graphic formed along the strip material and the next graphic to be formed by comparing a positive graphic already formed on the strip material and a negative image of the next graphic to be formed on the template portion at the exposure station, which comparison causes difficulty in making manual adjustments that may be desirable for better appearing spacing between adjacent letters, especially between those letters which do not have vertical adjacent edges.